WASHINGTON — The stacks of Supreme Court briefs filed on both sides of the same-sex marriage cases to be heard this month are roughly the same height. But they are nonetheless lopsided: There are no major law firms urging the justices to rule against gay marriage.

Leading law firms are willing to represent tobacco companies accused of lying about their deadly products, factories that spew pollution, and corporations said to be complicit in torture and murder abroad. But standing up for traditional marriage has turned out to be too much for the elite bar. The arguments have been left to members of lower-profile firms. …

When the Supreme Court hears arguments on April 28 in the marriage cases, among them Obergefell v. Hodges, No. 14-556, the main lawyer opposing same-sex marriage will be John J. Bursch, who practices at a medium-size firm in Michigan. He served as the state’s solicitor general and has argued eight cases in the Supreme Court. But his firm, Warner Norcross & Judd, will not be standing behind him. …

Mr. Bursch’s experience was similar to that of Paul D. Clement, who served as solicitor general in the George W. Bush administration and has argued more than 75 cases in the Supreme Court. He defended a federal law, the Defense of Marriage Act, that denied benefits to married same-sex couples, losing in the Supreme Court in 2013 by a 5-to-4 vote. He is conspicuously absent this time around.

Mr. Clement seems to have learned a bitter lesson from the last case, United States v. Windsor. In 2011, as it was heating up, his law firm, King & Spalding, withdrew from the case under pressure from gay rights groups. Mr. Clement quit, moving to a smaller firm and continuing to represent his clients.

“I resign out of the firmly held belief,” he wrote at the time, “that a representation should not be abandoned because the client’s legal position is extremely unpopular in certain quarters.” Mr. Clement did not respond to a request for comment.

Ryan T. Anderson, a fellow at the Heritage Foundation who opposes same-sex marriage, said the episode was a turning point. “When the former solicitor general and superstar Supreme Court litigator is forced to resign from his partnership,” Mr. Anderson said, “that shows a lot.”

Gay rights advocates offer their own reason for why prominent lawyers are lined up on one side of the marriage cases. “It’s so clear that there are no good arguments against marriage equality,” said Evan Wolfson, the president of Freedom to Marry. “Lawyers can see the truth.”

Mr. Wolfson would make a fine lynch law lawyer.

The current attitude among elite lawyers about same-sex marriage grew very quickly, said Kenji Yoshino, a law professor at New York University.

The current climate, Professor McConnell of Stanford said, means that important distinctions are being lost. One is that it is possible to favor same-sex marriage as a policy matter without believing that the Constitution requires it. …

But this is, he said, a topic he has learned to avoid. “You’re going to shut up, particularly if you don’t care that much,” he said. “I usually just keep it to myself.”